Electrical fence



J1me 1967 w. M. NELLIS 3,325,717

ELECTRICAL FENCE Original Filed March 6, 1965 INVENTOR. b mdzam 1% 11/ 1/59 BY M $3M, W 737 WW I A 'ITUR [5 Y8 United States Patent ELECTRICAL FENCE William M. Nellis, St. Paul, Minn., assignor to International Electric Fence Company, Inc., Albert Lea, Minn.,

a corporation of Washington I Continuation of application Ser. No. 263,346, Mar. 6,

1963. This application Apr. 6, 1966, Ser. No. 547,692 1 Claim. (Cl. 321-2) This application is a continuation of my copending application entitled, Fence Charger, Ser. No. 263,346, filed Mar. 6, 196 3.

This invention relates to an electrically charged fence circuit.

Known fence chargers have several disadvantages. In one form, there is a motor-driven switch, in another form there is employed a tilting mercury switch, in another form a steel ball oscillates back and forth, and in a still further form an extremely high potential is built up in a capacitor which is discharged. All of these devices include a substantial number of parts. At least three of these types or structure embody moving parts which are subject to wear, and deterioration, and all of these types have been so constructed that they are adversely affected by ambient weather conditions. This has necessitated maintenance and/or replacement of affected components. Further, it has been possible for someones hands to come in contact with a component thereof and get a severe shock, even when the fence charger has been disconnected with the source of power.

The present invention utilizes as few. as three components in addition to the fence and employs only solid state components, the same being preferably encapsulated to protect them from environmental factors such as high humidity, dust, and the like. Moreover, the high potential which appears ultimately on the fence is induced by an inductively created pulse, and does not, as such, originate directly from the discharge of a high potential capacitor.

Accordingly, it is an object of the present invention to provide an electrically charged fence circuit.

Another object of the present invention is to provide an electricaly charged fence circuit which employs no movable parts.

A further object of the inventionis to provide a fence which is electrically charged by a circuit employing only a D.C.-charged capacitor, a 4-layer diode, and a transformer.

Yet another object of the present invention is to provide a fence charge which is resistant to variations in environmental factors.

A still further object of the present invention is to provide a fence charger wherein no high potential is built up and stored, thereby eliminating a hazard which might be encountered by personnel, even though the device is disconnected from the power line.

Many other advantages, features and additionalobjects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying drawing sheet in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

On the drawing:

The single figure is a schematic diagram of an electrica-lly charged fence circuit provided in accordance with the principles of the present invention.

As shown on the drawing:

The principles of this invention are particularly useful when embodied in an electrically charged fence such as illustrated in the figure, generally indicated by the numeral 10. The charged fence circuit includes an Patented June 13, 1967 output transformer 11 connected to a fence 12, which is periodically energized by a circuit generally indicated at 13.

The output transformer 11 has a secondary-to-primary winding ratio of 60:1, so that when a 50 'volt input is applied to the primary winding 14, there will be a 3000 volt output induced in a secondary winding 15. One side of the secondary winding 15 is provided with a' terminal 16 for connection to ground, and the other side of the secondary winding 15 is provided with a terminal 17 connected to the fence 12. The secondary circuit is completed when an animal engages the fence 12 while standing on earth ground, such animal being represented by the resistance 18 which typically has a value in the general range of 10,000 ohms to 1,000 ohms.

The circuit 13 is periodically operative to send a lowvoltage high-amperage current pulse through the primary winding 14 of the transformer 11 whereby the high-voltage current pulse which is induced in thesecondary winding is of low amperage.

The circuit 13 includes an input circuit 19 having a unidirectiona-lly charged capacitor 20. To this end, the input circuit 19 includes a source of direct current such as a half-wave rectifier 21 and a resistor 22, and the capacitor 20, all connected in series with each other and to a pair of terminals 23, 24, one of which is connected through a fuse 25 to one side of a 60.cycle A.C.-power supply and the other one of which terminals is connected to the other side of the power supply. Where a D.C.-power supply is used, it may be connected directly across the capacitor 20. t

The circuit 13 further includes a normally non-conducting. circuit 26 connected across the capacitor 20 and including an electronic switch 27 connected. in series with the primary winding 14.

' The electronic .switch 27 comprises a 4-layer. diode means of the PNPN type.

When the input circuit 19 is connected to a power supply, unidirectional current acts to charge the capacitor 20 unidirectionally at .a rate determined by the capacitance of the capacitor 20, as well as the resistor 22. The voltage across the capacitor 20 also appears across the 4- layer diode 27, whichis normally non-conducting. Hence no current is normally flowing in the primary winding 14 of the transformer, and no charge is present on the fence 12. However, when the charge on the capacitor 20 reaches a predetermined level, a voltage threshold value for the 4-layer diode 27 is reached which is a critical value that renders it conductive, whereby the normally nonconducting circuit 26 short-circuits the capacitor 20 to discharge it in a single direction determined by the diode 27 which also acts as a rectifier, in that it permits current flow in a single direction. This current flow passes through the primary winding 14. The voltage charge on the capacitor 20 is relatively low, and its capacitance is 'adequateto provide a substantial momentary current flow which is relatively high, which passes through the primary winding 14.

A particularly important feature of the present invention is the utilization of the 4-layer diode 27 in the circuit. This diode is responsive to a predetermined charge on the capacitor to render it conductive, and once it has been rendered conductive, it is responsive to a predetermined lesser current flow therethrough, largely independent of voltage across it, for re-establishing the non-conductive condition.

T 0 protect the diode 27 from possible damage due to any tendency for current to flow momentarily in a reverse direction at the end of the discharge, a further resistor 28 may be employed in series with the 4-layer diode 27 and the primary winding 14.

The values presented below are such that the capacitor 20 will become charged, in approximately one second, to the critical potential of the 4-layer diode 27. The discharge of the capacitor 20 will take place through the winding 14 in three or four milliseconds. With the transformer primarily designed to provide critical damping of the circuit 26, the timing thus described is dependable and is constant for all practical purposes.

The capacitor 20, the half-Wave of rectifier 21, the resistor 22, the 4-1ayer diode 27, and preferably the resistor 28 are preferably encapsulated as a unit in epoxy resin, for example type 241 or type 250 made by Minnesota Mining & Manufacturing Co., the terminals 23 and 24 projecting therefrom for connection to the AC-power supply, and a pair of terminals 29 and 30 projecting therefrom for connection to a pair of terminals 31 and 32 leading to the primary winding 14 of the transformer 11.

The device further preferably includes a gas discharge glow tube 33, such as of the neon type, connected in series with a high resistance 34 and across the secondary winding 15. Each time that a pulse is applied to the fence 12, the glow tube 33 will also momentarily become ignited. Thus, when pulses are being induced in the secondary winding 15, an absence of ignition will indicate that the fence 12 is shorted to ground.

. Circuit components in a typical embodiment are sized as follows:

The half-wave rectifier 21 should have a 500 milliampere direct current rating and 300-volt peak inverse voltage rating. The resistor 22 has a resistance 1750 ohms and a -watt rating. The capacitor 20' has a 250 mfd. capacitance and 50-volt rating. A typical 4-layer diode 27 is the Clevite 4E50. The size of the resistor 28 is determined experimentally depending on the primary winding 14 employed. The resistor 34 has a 500,000 ohm halfwatt rating. The gas discharge tube 33 has a typical ignition potential of 70 volts.

" In the operation of the device, the 4-layer diode 27 is non-conducting during the charging of the capacitor 20 until the voltage thereon has built up to the switching voltage of the 4-layer diode 27, which in each instance will be less than the potential of the power supply. Once the diode 27 is rendered conductive, it has a lesser resistance, so that theoretically current could flow from the half-wave rectifier, directly to the diode 27 and the winding 14, and return by means of the path through the terminals 32 and '24. However, the source of potential does not keep the diode 27 in a conducting state since the 4-layer diode 27 is responsive to a decrease in the magni tude of current flow to a level below that needed to hold it in a conductive state. With a complete discharge of the capacitor 20 this critical value of holding current is no longer maintained and the diode 27 becomes non-conductive even though it is still subject to successive unidirectional voltage pulses.

Accordingly, it is seen that the present circuit includes no moving parts, includes no capacitor charged to a high potential at any time, and provides a fixed amount of energy which is adequate to be effective for an electric fence, but is not a hazard to animal or human life.

By encapsulation, protection is provided against deterioration or malfunction clue to humidity or other moisture,

and there is an indication means provided for detecting whether the fence is short circuited.

Although various rninor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent war-ranted hereon all such embodiments as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

An electrical fence assembly, comprising:

(a) an elongated fence which normally is non-energized;

(b) an output transformer having a normally nonenergized secondary winding connected to said fence, and a primary winding;

(c) a 4-1ayer diode having only two terminals, and a capacitor connected in series with eachother and across said primary winding, said 4-layer diode normally rendering said primary winding totally nonconductive, and said 4-layer diode having a voltage threshold property rendering the primary winding highly conductive in direct response to a predetermined voltage charge of harmless magnitude on said capacitor to discharge it through said primary winding to momentarily energize said secondary winding, and having a current threshold property .by which it renders said primary winding non-conductive in response to a predetermined lesser capacitor-discharge current flow through said primary winding substantially independent of voltage;

(d) means connected across said capacitor for unidirectional charging it;

(e) a resistor being connected in series with said 4- layer diode at a point where capacitor-discharge current flows therethrough; and

(f) said charging means including a solid-state rectifier and a series resistor which with said capacitor and said 4-layer diode form an epoxy-resin-encapsulated sub-assembly, said sub-assembly being connected as a unit to said transformer.

References Cited UNITED STATES PATENTS 2,343,300 3/1944 Klumb 256-10 2,767,331 10/1956 Hurst et al. 307-432 2,985,812 5/1961 Peterson 32115 3,157,829 11/1964 Wood.

I FOREIGN PATENTS 856,041 12/1960 Great Britain.

OTHER REFERENCES Non-Linear Diode Logical Circuits, IBM Technical Disclosure Bulletin, vol. 1, No. 6, April 1959, pp. 27, 28.

PNPN Transistor Switches," Proceedings of the IRE, September 1956, pp. 1174-1182.

Pulse and Digital Circuits, Mil-lman and Taub, McGraw Hill Book Company 1956.

JOHN F. COUCH, Primary Examiner.

W. H. BEHA, Assistant Examiner. 

